Wound dressing with vacuum reservoir

ABSTRACT

A wound dressing apparatus includes a wound dressing member dimensioned for positioning relative to a wound bed. The wound dressing member including an internal vacuum reservoir and has a port in communication with the vacuum reservoir for applying subatmospheric pressure to the vacuum reservoir to facilitate removal of fluid from the wound bed. The wound dressing member includes a visual pressure indicator associated therewith for indicating a level of pressure within the vacuum reservoir. The visual pressure indicator includes color indicia having a plurality of colors corresponding to a condition of the pressure within the vacuum reservoir. The wound dressing member includes a lower absorbent member positionable adjacent the wound bed and an upper member which at least partially defines the vacuum reservoir. At least one of the top member and the lower absorbent member has the visual pressure indicator mounted thereto.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional application of U.S. patentapplication Ser. No. 11/516,925, filed on Sep. 6, 2006, which claims thebenefit of U.S. Provisional Patent Application No. 60/714,805, filed onSep. 7, 2005, now abandoned, the entire contents of each areincorporated herein by this reference.

BACKGROUND 1. Technical Field

The present disclosure relates to an apparatus for treating an openwound, and, more specifically, relates to a wound dressing that drawswound fluids into a vacuum reservoir to facilitate the wound healingprocess.

2. Description of Related Art

Wound closure involves the migration of epithelial and subcutaneoustissue adjacent the wound towards the center of the wound until thewound closes. Unfortunately, closure is difficult with large wounds orwounds that have become infected. In such wounds, a zone of stasis (i.e.an area in which localized swelling of tissue restricts the flow ofblood to the tissues) forms near the surface of the wound. Withoutsufficient blood flow, the epithelial and subcutaneous tissuessurrounding the wound not only receive diminished oxygen and nutrients,but, are also less able to successfully fight microbial infection and,thus, are less able to close the wound naturally. Such wounds havepresented difficulties to medical personnel for many years.

Wound dressings have been used in the medical industry to protect and/orfacilitate healing of open wounds. One popular technique has been to usenegative pressure therapy, which is also known as suction or vacuumtherapy. A variety of negative pressure devices have been developed toallow excess wound fluids, i.e., exudates to be removed while at thesame time isolating the wound to protect the wound and, consequently,reduce recovery time. Various wound dressings have been modified topromote the healing of open wounds.

Issues that continually need to be addressed when using a wound dressinginclude ease of use, efficiency of healing a wound, and the source ofconstant or varying negative pressure. Thus, there remains a need toconstantly improve negative pressure wound dressings for open wounds.

SUMMARY

In one preferred embodiment, a wound dressing apparatus includes a wounddressing member dimensioned for positioning relative to a wound bed. Thewound dressing member includes an internal vacuum reservoir and having aport in communication with the vacuum reservoir for applyingsubatmospheric pressure to the vacuum reservoir to facilitate removal offluid from the wound bed. The wound dressing member includes an accessdoor associated therewith and being selectively movable between a closedposition substantially enclosing the vacuum reservoir and an openposition permitting access to the vacuum reservoir.

The wound dressing member preferably includes a lower absorbent memberwhich is positionable adjacent the wound bed and an upper member. Theupper member at least partially defines the vacuum reservoir. The accessdoor is mounted to the upper member. The lower member may comprise amaterial selected from the group consisting of foams, nonwoven compositefabrics, cellulosic fabrics, super absorbent polymers, hydrogels andcombinations thereof. The lower member also may include at least one ofa medicament, an anti-infective agent, an antimicrobial, such aspolyhexamethylene biguanide (hereinafter, “PHMB”), antibiotics,analgesics, healing factors, vitamins, growth factors, debridementagents and nutrients. The wound dressing member may include an adhesivemember which is adapted to be secured about the wound bed to provide aseal between the wound dressing member and tissue surrounding the woundbed.

The wound dressing apparatus may further include a vacuum source influid communication with the port. The vacuum source is adapted tosupply subatmospheric pressure in a range between about 20 mmHg andabout 500 mmHg to the vacuum reservoir. The port may include valvemeans.

The wound dressing member may include a visual pressure indicator forindicating a level of pressure within the vacuum reservoir. Thepreferred visual pressure indicator includes color indicia whichcorrespond to a condition of the subatmospheric pressure within thevacuum reservoir. The preferred visual pressure indicator includes aposition sensor. The visual pressure indicator may include circuit meansand visible alarm means. The circuit means is adapted to actuate thevisible alarm means when the position sensor detects a relativepositioning of the top member of the wound dressing member to provide avisual indication of the condition of the subatmospheric pressure withinthe vacuum reservoir.

In another embodiment, a wound dressing apparatus includes a wounddressing member dimensioned for positioning relative to a wound bed. Thewound dressing member including an internal vacuum reservoir and has aport in communication with the vacuum reservoir for applyingsubatmospheric pressure to the vacuum reservoir to facilitate removal offluid from the wound bed and stimulate wound healing. The wound dressingmember includes a visual pressure indicator associated therewith forindicating a level of pressure within the vacuum reservoir. The visualpressure indicator may include color indicia having a plurality ofcolors corresponding to a condition of the pressure within the vacuumreservoir. The wound dressing member includes a lower absorbent memberpositionable adjacent the wound bed and an upper member which at leastpartially defines the vacuum reservoir. At least one of the top memberand the lower absorbent member has the visual pressure indicator mountedthereto. The visual pressure indicator may include an electronicposition sensor. The visual pressure indicator may further includecircuit means and visible alarm means. The circuit means is adapted toactuate the visible alarm means when the position sensor detects arelative positioning of the top member of the wound dressing member toprovide a visual indication of the condition of the subatmosphericpressure within the vacuum reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject wound dressing are described hereinwith reference to the drawings wherein:

FIG. 1 is a side cross-sectional view of the wound dressing apparatus inaccordance with the principles of the present disclosure on a wound bed;

FIG. 2 is a view similar to the view of FIG. 1 illustrating the wounddressing subjected to subatmospheric pressure;

FIG. 3 is a top view of the wound dressing;

FIG. 4 is a view similar to the view of FIG. 2 illustrating the accessdoor in an open condition to permit access to the internal vacuumreservoir;

FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 3illustrating the visual pressure indicator;

FIG. 6 is a block diagram illustrating the components of the electronicvisual indicator device;

FIG. 7 is a view similar to the view of FIG. 1 illustrating an alternateembodiment of the present disclosure;

FIG. 8 is a view illustrating an alternate visual indicia arrangement ofthe visual indicator device;

FIG. 9 is a side cross-sectional view of an alternate wound dressing ona wound bed and in the absence of a vacuum;

FIG. 10 is a view similar to the view of FIG. 9 illustrating the wounddressing in a contracted condition when subjected to subatmosphericpressure; and

FIG. 11 is a top view of the wound dressing of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The composite wound dressing of the present disclosure promotes healingof a wound via the use of a vacuum reservoir. The vacuum reservoirsubjects the wound to vacuum or subatmospheric pressure to effectivelydraw wound fluid including liquid exudates from the wound bed withoutthe continuous use of a vacuum source or pump. Hence, vacuum pressurecan be applied once or in varying intervals depending on the nature andseverity of the wound until the composite wound dressing is saturatedwith exudate or the wound is healed. If the wound dressing is saturatedwith exudate and the wound is not healed, certain and/or all layers ofthe composite wound dressing can be replaced and the process of applyingsubatmospheric pressure can be repeated.

Referring now to FIGS. 1-3, the composite wound dressing 100 inaccordance with a preferred embodiment of the present disclosure isillustrated in the form of an article with multiple layers arranged injuxtaposed or superposed relation. The multiple layers include, but, arenot limited to a lower or base layer 102, an absorbent/packing layer104, an adherent layer 106, and a top layer 108 which includes and/ordefines the internal vacuum reservoir 110.

The base layer 102 is in direct contact with the wound bed “w”. The baselayer 102 is typically porous allowing passage of subatmosphericpressure to the wound bed. In one preferred embodiment, the base layerincludes a “non-adherent” material. “Non-adherent” as used herein refersto a material that does not adhere to tissues in and around the woundbed. “Porous” as used herein refers to a material which containsnumerous small perforations or pores which allow wound fluids of allkinds to pass through the material to the dressing layers above. Thepassage of wound fluid through the porous material may be unidirectionalsuch that wound exudate does not flow back to the wound bed. Thisdirection flow feature could be in the form of directional aperturesimparted into the material layer, a lamination of materials of differentabsorption to the base layer 102 or specific material selection thatencourages directional flow. Exemplary materials used as the base layer102 include a contact layer sold under the trademark XEROFLOW® byKendall Corp., a division of TycoHealthcare. In the alternative, thebase layer 102 may include an adherent material.

In addition, agents such as hydrogels and medicaments could be bonded orcoated to the base layer 102 to reduce bioburden in the wound, promotehealing and reduce pain associated with dressing changes or removal.Medicaments include, for example, antimicrobial agents, growth factors,antibiotics, analgesics, debridement agents and the like. Furthermore,when an analgesic is used, the analgesic could include a mechanism thatwould allow the release of that agent prior to dressing removal orchange. Exemplary triggers of a release mechanism could be temperaturechange.

The layer proximal to the base layer 102 or composite structures makingthe base layer 102 is the absorbent/packing layer 104. Theabsorbent/packing layer 104 of the wound dressing 100 is intended toabsorb and capture wound fluid and exudates. Exemplary absorbentmaterials include foams, nonwoven composite fabrics, hydrogels,cellulosic fabrics, super absorbent polymers, and combinations thereof.Typically, the absorbent/packing layer 104 can absorb up to about 100cubic centimeters (cc) or more of wound fluid. Preferably, the absorbentmaterial includes the antimicrobial dressing sold under the trademarkKERLIX® by Kendall Corp., a division of TycoHealthcare. In one preferredembodiment, the absorbent/packing layer 104 could be preformed or shapedto conform to varying shapes of the wound bed. Those skilled in the artwill recognize that the absorbent/packing layer 104 can be formed in anysuitable shape. Absorbent/packing layer 104 may include multiple layers.The only requirement as to shape is that the absorbent/packing layer 104is suitable to treat a particular shape of the wound.

Additionally, the absorbent/packing layer 104 could be treated withmedicaments. Medicaments include, for example, an anti-infective agentsuch as an antiseptic or other suitable antimicrobial or combination ofantimicrobials, polyhexamethylene biguanide (hereinafter, “PHMB”),antibiotics, analgesics, healing factors such as vitamins, growthfactors, nutrients and the like, as well as a flushing agent such asisotonic saline solution.

With continued reference to FIGS. 1-3, the adherent layer 106 at leastencompasses the perimeter of the wound dressing 100 to surround thewound bed to provide a seal around the perimeter of the wound bed “w”.For instance, the sealing mechanism may be any adhesive bonded to alayer that surrounds the wound bed “w” or an adhesive applied directlyto the skin. The adhesive must provide acceptable adhesion to the tissue“t” surrounding the wound bed “w” skin, e.g., the periwound area, and beacceptable for use on skin without contact deterioration (for example,the adhesive should preferably be non-irritating and non-sensitizing.)The adhesive may be semi-permeable to permit the contacted skin totransmit moisture or may be impermeable. Additionally, the adhesivecould be activated or de-activated by an external stimulus such as heator a given fluid solution or chemical reaction. Adhesives include, forexample, the dressing sold under the trademark ULTEC® Hydrocolloiddressing by Kendall Corp., a division of TycoHealthcare.

The adherent layer 106 may also be in the form of an entire layerproximal to the absorbent/packing layer 104 or preferably is annular or“donut shaped” as shown. Preferably, the adherent layer 106 is notbonded to the absorbent/packing layer 104 to allow for easy replacementof the absorbent/packing layer 104. In a preferred embodiment, theadherent layer 106 is at least bonded to the periphery of the base layer102. In turn, the peripheral portion 108 a of the top layer 108 may bebonded to the adherent layer 106 to provide a seal around the perimeterof the wound. Alternatively, the adherent layer 106 may be positioned onthe peripheral portion 108 a of the top layer 108 and secured to thetissue “t” about the wound bed “w”, and not bonded to the base layer102. As a further alternative, the peripheral portion 108 a of the toplayer 108 may include an adhesive surface. It is anticipated thatremovable contact liners may also be used to protect the adhesivesurface of the adherent layer 106 prior to use.

The top or upper layer 108 typically seals the top of the wound dressing100 and helps maintain the appropriate vacuum level within the wounddressing 100. In one preferred embodiment, the top layer 108 includesthe flexible transparent dressing manufactured under the trademarkPOLYSKIN® II by Kendall Corp., a division of TycoHealthcare. POLYSKIN®II is a transparent, semi-permeable material which permits moisture andoxygen exchange with the wound site, and provides a barrier to microbesand fluid containment. In the alternative, the top layer 110 may beimpermeable. As a further alternative, the top layer 108 may include aresilient, e.g., elastomeric, material in the shape, e.g., of a dome.

The top layer 108 defines a sealed or enclosed vacuum reservoir 110. Thevacuum reservoir 110 is preferably maintained at an appropriate vacuumlevel for a predetermined period of time sufficient to initiate orcomplete healing of the wound bed “w”, i.e., to draw wound fluid andexudate away from the wound bed “w” while subjecting the wound tosubatmospheric pressure. The vacuum may be re-applied as needed tomaintain a therapeutic effect. The vacuum may be continuous orintermittent as desired.

As best seen in FIG. 1, the vacuum reservoir 110 is defined within thedome of the top layer 108. As shown in FIG. 2, once vacuum is applied,the dome of the top layer 108 is drawn downwardly toward theabsorbent/packing layer 104 with the vacuum or subatmospheric reservoir110 created beneath the top layer 108. Typically, the top layer 108includes a vacuum port or connector 114 in fluid communication with thevacuum reservoir 110. Preferably, the vacuum port 114 includes a one-wayvalve (shown schematically as reference numeral 116) which providesunidirectional flow of suction and may provide a means for allowingconnection of the composite wound dressing 100 to the vacuum source 112.The one way valve 116 may be incorporated within the vacuum port 114 or,alternatively, be “in line” with the vacuum source 112. A flexibletubing 118 is connected to the vacuum port 114 and the vacuum source112. The tubing 118 provides suction to the wound from the vacuum source112 and enables the wound fluid to be transferred from the wounddressing 100. The tubing 118 may be fabricated from PVC, silicone basedmaterial or other flexible materials (polymers). The tubing 118 mayoptionally include a connection to a collection canister 120 for wounddrainage and debris. Hence, the vacuum source 112 can draw wound fluidthrough the composite wound dressing 100 and tubing 118 into thecanister 120. In a preferred embodiment of the present disclosure, thecanister 120 is portable so that the patient will have the freedom tomove about rather than being confined to a fixed location. The canister120 may also house an absorbent material to absorb wound fluid andexudate.

The vacuum source 112 may apply vacuum to the wound by means such as amanual pump as disclosed in commonly assigned U.S. Pat. No. 5,549,584 toGross, the entire contents of which are hereby incorporated herein byreference. In the alternative, the vacuum source 112 may include anautomated pump. Typically, the vacuum level is in a range between about20 mmHg to about 500 mmHg, more preferably, about 40 mmHg and about 125mmHg. The automated pump may be a wall suction apparatus such as thoseavailable in an acute or sub-acute care facility. The automated pump maybe in the form of a portable pump. The portable pump may include a smallor miniature pump that maintains or draws adequate and therapeuticvacuum levels. In a preferred embodiment, the pump is a portable,lightweight, battery operated, suction pump which attaches to the distalend of the tubing. Typically, the vacuum source 112 has regulation meansto apply the optimal vacuum pressure for healing the wound. Furthermore,the vacuum source 112 would preferably contain a mechanism to detect aleak in the system if the optimal vacuum pressure is not achieved.Preferably, the vacuum source 112 would also contain an indicator (notshown) to indicate when the optimal vacuum pressure is achieved. In thealternative, a hand pump in the form of a squeeze bulb or a foot pumpmay serve as the vacuum source 112.

Preferably, a pump is used as the vacuum source 112. Typical pumpsinclude diaphragm or voice coil activated styles that can delivervariable vacuum up to 50 cc/minute.

With reference now to FIGS. 1-4, the top layer 108 may include an accessdoor 122 to provide access to the interior of the wound dressing 100and/or the wound bed “w”. The door 122 could be a flap integrally formedwith the top layer 108 or a separate component connected to the toplayer 108 via a hinge or the like. The door 122 is preferably resealableto maintain the integrity of the vacuum reservoir 110 and provide a sealrelative to the top layer 108. One suitable means for releasably sealingthe door 122 includes a snap fit arrangement, tongue and groovearrangement, “Zip Lock®” arrangement, adhesives, VELCRO®, etc. The door122 preferably provides access to the wound bed “w” to enable theclinician to monitor the status of the wound, change theabsorbent/packing layer 104, or apply additional medical treatment tothe wound such as antimicrobial agents, growth factors, debriders, orother wound healing agents as needed. Once the desired procedure iscompleted, the door 122 would be resealed relative to the top layer 108to maintain the integrity of the vacuum reservoir 110. FIG. 4illustrates the removal of the absorbent/packing layer 104 through thedoor 122 when the door 122 is in an open position. As discussed, a newabsorbent/packing layer 104 subsequently may be introduced through thedoor 122 to absorb the exudates from the wound bed “w”.

With reference now to FIGS. 3 and 5, in conjunction with FIGS. 1-2, thewound dressing 100 may include a visual indicator device 124 mounted tothe top layer 108 to provide a visual indication of vacuum pressurewithin the wound dressing 100. The visual indicator device 124 mayinclude at least one electronic position indicator for detecting therelative position of the top layer 108 and the wound bed, and, thus thestate of the vacuum within the wound dressing 100. In accordance withthis embodiment, the top layer 108 may have a resilient characteristiceither through the material of construction of the top layer 108 orthrough reinforcement (e.g., elastomeric) members incorporated in thetop layer 108.

In one embodiment depicted in FIG. 6, the visual indicator device 124includes at least one, preferably, three position-sensitive switches 126a-126 c, and a self-powered electronic signaling module 128. The module128 may include an electronic signaling module circuit board 130, abattery power source 132, at least one transducer including three lightemitting diodes (LED) 134 a-c and/or a loudspeaker 136 electricallyconnected 138 to the circuit board 130. The LEDs 134 a-c are color codedred, yellow and green respectively. The position-sensitive switches 126a-126 c each may be a pressure sensor which electrically bridgescontacts 140 a, 140 b of the visual indicator device 124.

In the embodiment shown, three position switches 126 a-c are mounted totop layer 108. The switches 126 a-c include switch plates or contactarms arranged as a series of decreasing diameter annular coaxialelements. Alternatively, the switches may be linear in configurationdepending downwardly from the top layer 108. The switch plate or contactarm of switches 126 a-c are of predetermined length extending downwardlyfrom the top layer 108 within the vacuum reservoir 110. (FIGS. 4 and 5)The contact arm of outer switch 126 a of the pressure indicator 124 hasthe greatest length. The contact arm of the middle switch 126 b has alength less than the length of the contact arm of the outer ring 126 a.The contact arm of the inner switch 126 c has the smallest length. Thecontacts 140 a of switches 126 a-c are integrated within the contactarms. Contacts 140 b of the switches 126 a-c may be disposed on the topsurface of the absorbent/packing layer 104 or integrated within theabsorbent/packing layer 104 in general longitudinal alignment with theirrespective contact arms. Alternatively, the position sensor may be amagnetic proximity sensor. The self-powered electronic signaling module130 may be any conventional modules adapted to emit light and/or audiblesound etc. upon closing of the switch.

When the top layer 108 is drawn down by vacuum pressure within thevacuum reservoir 110 toward its vacuum state of FIG. 2, inner switch 126c is in contact with a respective coupler or contact 140 b disposedwithin the absorbent/packing layer 104 thereby energizing the visualindicator device 124 to illuminate the green LED 134 c within thepressure indicator device mounted to the top layer 108. The green lightof the LEDs 134 c indicates a full vacuum condition of the vacuumreservoir 110. As appreciated, switches 126 a, 126 b may also be incontact with their respective couplers in this vacuum condition of toplayer 108. However, it is envisioned that circuit board 130 willincorporate circuitry to override the electrical contact of these twoswitches when switch 126 c is in contact with its respective coupler.

As vacuum pressure decreases and the dome of the top layer 108 begins toassume its normal condition of FIG. 1, through, e.g., the resilientcharacteristic of the top layer 108 discussed hereinabove, the innerswitch 126 c loses contact with the absorbent/packing layer 104 whilethe middle switch 126 b maintains/establishes electrical contact withits associated contact 140 b. The electrical connection of the middleswitch 126 b results in illumination of the yellow LED 134 b. The yellowLED 134 b represents a partial vacuum or marginal vacuum condition ofthe vacuum reservoir 110. As the vacuum pressure further decreases andthe top layer 108 moves towards its fully expanded or normal conditionof FIG. 1, the outer switch 126 a is the remaining switch in contactwith its associated contact 140 b within the absorbent/packing layer104. In this condition, the red LED 134 a is energized and visible tothe clinician essentially providing a warning that the vacuum within thevacuum reservoir has dissipated or is nearly dissipated (i.e.,subatmospheric pressure is close to or no longer present). Consequently,the vacuum source 112 may be actuated either manually or automaticallyto reestablish the vacuum state within the vacuum reservoir 110. Furthervacuum loss will result in the remaining switch 126 c losing its contactwhere no lights are visible to the patient.

It is also envisioned that the circuit board 130 could be devoid of theaforementioned override circuitry. As a result, in the full vacuumcondition of dressing 100, each of the green, yellow and red LEDs 134a-134 c would be illuminated while in the partial vacuum state, theyellow and red LEDs 134 a, 134 b would be illuminated and in the warningstate, the red LED 134 a would be illuminated. It is further envisionedthat the loudspeaker 136 could emit an audible alarm when any of theaforementioned vacuum states are realized.

FIG. 7 illustrates an alternate embodiment of the visual pressureindicator 124. In accordance with this embodiment, the visual pressureindicator 124 is mounted to the absorbent/packing layer 104 orpositioned on the absorbent/packing layer 104 in juxtaposed relation.The top layer 108 is preferably transparent to permit viewing of thepressure indicator 124 through the top layer 108 and into the vacuumreservoir 110. The positioning of the visual pressure indicator 124 isreversed or arranged on its back in a manner where the respectiveswitches 126 a-c extend upwardly toward top layer 108. The respectivecoupler or contacts 140 b are incorporated within the top layer 108. Inthe full vacuum state or condition of FIG. 2, the contact 140 b of thetop layer 108 is in contact with the switch 126 c thereby energizing theLED 134 c to display the green color to the clinician. During healing,as the vacuum reservoir begins to lose its vacuum, the top layer 108moves towards its open condition of FIG. 1, the inner switch 126 c losesits contact with its respective coupler 140 b of the top layer 108resulting in electrical contact with the yellow LED 134 b indicating apartial vacuum condition of the vacuum reservoir 110. Continued loss ofvacuum within the vacuum reservoir 110 causes the electrical contact ofthe coupler 140 b with the outer switch 126 c. This contact of the LED134 c with the outer switch 126 c is indicated by the presence of itsred color and may correspond to a loss or near loss of vacuum within thevacuum reservoir 110 thus prompting the clinician to activate the vacuumsource 112 or pursue other clinical measures.

FIG. 8 illustrates another embodiment where the LEDs 134 a-134 c aresupplemented with additional visual indicia. The visual indicia mayinclude various symbols which correspond to the state of the vacuumwithin the vacuum reservoir 110. When a desired level of vacuum isreached, the “smiley” symbol 152 would illuminate indicating an adequatevacuum state. A partial vacuum state would result in the illumination ofthe “caution triangle” symbol 154. A loss or near loss of vacuum wouldresult in the illumination of the “octagon” symbol (no vacuum) 156. Oneskilled in the art will readily appreciate the design of electroniccircuitry to achieve this objective.

FIGS. 9-11 illustrate an alternate embodiment of the present disclosure.In accordance with this embodiment, the visual indicator device 124 mayinclude a series of rings 200,202,204 disposed on the underside of thetop layer 108, e.g., printed on the top layer 108, and arranged inconcentric relation as shown. The rings include outer ring 200, middlering 202 and inner ring 204 and are color coded red, yellow and green,respectively. Each colored ring 200,202,204 is positioned to contact theabsorbent/packing layer 104 depending on the state or condition of thevacuum within the vacuum reservoir 110. Under full vacuum depicted inFIG. 10, all the rings 200,202,204 would contact absorbent/packing layer104 and thus be activated and visible through the top of the wounddressing. As the vacuum within the reservoir dissipates or is reduced,the top layer 110 pulls away from the absorbent/packing layer 104. Inone embodiment with an elastomeric dome, the inner ring 204 first losescontact followed by the middle and outer rings, 202, 200, respectively,as the vacuum is reduced. As each colored ring 200,202,204 loses contactwith absorbent/packing layer 104, the respective ring becomes lessvisible or not visible from above the wound dressing 100 thus indicatingto the clinician the condition of the vacuum within the vacuumreservoir. The rings 200,202,204 may incorporate electronic switches tobe activated in the manner discussed hereinabove in connection with theembodiment of FIGS. 1-6. Alternatively, each ring 200,202,204 mayincorporate an analytical test strip device which, e.g., may detect thepresence of a predetermined analyte in the exudates contained in theabsorbent/packing layer 104. Upon contact with the predeterminedanalyte, the test strip device of each ring 200,202,204 assumes a colorsuch as red, yellow or green. When a respective ring 200,202,204 losescontact with the predetermined analyte, the color of the respective ringmay fade or assume a neutral color. One exampled of a color coded teststrip device suitable for use with the present disclosure is disclosedin U.S. Pat. No. 7,049,130 to Carroll et al., issued May 23, 2006, theentire contents of which are incorporated herein by reference. Oneskilled in the art may determine the parameters and characteristics of atest strip device to perform the objectives discussed hereinabove.

In addition, the door 122 of the embodiment of FIGS. 9-11 is adapted topivot along hinge 208 to provide access to the vacuum reservoir 110. Theopening of the door 122 is disposed adjacent the periphery of the wounddressing 102 and thus provides a relatively large access opening uponpivoting or opening the door 122 along the hinge 208. This facilitatesremoval and replacement of absorbent/packing layer 104.

It is further contemplated that the wound dressing apparatus mayincorporate external means or applications to stimulate tissue growthand/or healing. For example, an ultrasonic transducer may beincorporated into the wound dressing apparatus to impart mechanicalenergy for the treatment of the tissue such as, for instance, directingthermal or vibratory energy on the wound area to stimulate healingand/or further encouraging exudates removal by vacuum and/or introducingvarious drugs into the human body through the skin. Other sensor typesare also contemplated for incorporation into the wound dressingapparatus including oxygen, chemical, microbial and/or temperaturesensors. The detection of oxygen adjacent the wound area would assistthe clinician in determining the status of wound healing. The presenceof an elevated temperature may be indicative of an infection.

While the disclosure has been illustrated and described, it is notintended to be limited to the details shown, since various modificationsand substitutions can be made without departing in any way from thespirit of the present disclosure. For example, it is envisioned thesubject matter of the commonly assigned U.S. patent application Ser. No.11/517,210, filed on Sep. 6, 2006, and which claims priority to U.S.Provisional Application Ser. No. 60/714,812, filed on Sep. 6, 2005, andthe subject matter of the commonly assigned U.S. patent application Ser.No. 11/516,216, filed on Sep. 6, 2006, and which claims priority toprovisional application No. 60/714,912, filed on Sep. 7, 2005, (theentire contents of each application being incorporated herein) may beincorporated into the present disclosure. As such, further modificationsand equivalents of the invention herein disclosed can occur to personsskilled in the art using no more than routine experimentation, and allsuch modifications and equivalents are believed to be within the spiritand scope of the disclosure as defined by the following claims.

1.-14. (canceled)
 15. A wound dressing apparatus for use in negativepressure wound therapy, comprising: a porous, non-adherent layerconfigured to be in direct contact with a wound; a wound cover layerdimensioned for positioning over the wound, wherein the wound coverlayer defines an internal vacuum reservoir when the wound cover layer ispositioned over the wound; an adhesive material on an underside of thewound cover layer on a peripheral portion of the wound cover layer, theadhesive material configured to be secured to tissue surrounding thewound; a nonwoven fabric layer positioned between the porous,non-adherent layer and the wound cover layer; and a connector on thewound cover layer in fluid communication with the internal vacuumreservoir and configured to be connected with a source of negativepressure.
 16. The wound dressing apparatus of claim 15, wherein theconnector extends into the vacuum reservoir.
 17. The wound dressingapparatus of claim 15, further comprising a removable contact linerattached to the adhesive material and configured to be removed prior touse of the wound dressing apparatus.
 18. The wound dressing apparatus ofclaim 15, further comprising a canister for collection of wound exudate,wherein wound exudate is removable from the nonwoven fabric layer viathe connector.
 19. The wound dressing apparatus of claim 15, wherein theporous, non-adherent layer further comprises at least one medicament.20. The wound dressing apparatus of claim 15, further comprising anadherent layer, wherein the adhesive material is on the adherent layer.21. The wound dressing apparatus of claim 20, wherein the adherent layerencompasses the perimeter of the wound dressing.